Like every other steroid, Winstrol reduces your natural testosterone levels. This is an unavoidable, intractable, inherent side effect of all steroids-you can't reduce, modify, or change it whatsoever.
To understand why, let's look at how your body produces testosterone:
Your testes (or ovaries in women) produce testosterone. If your "T" levels dip, a portion of the brain called the hypothalamus senses the decrease and releases a hormone called Gonadotropin-Releasing Hormone (GnRH).
The pituitary gland detects the increased GnRH levels and produces luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which trigger specialized cells in the testes known as Leydig cells to produce testosterone.
As testosterone levels rise, the hypothalamus produces less GnRH, testosterone production decreases, and the cycle repeats itself.
Assuming someone is otherwise healthy, this system does a remarkably good job of keeping testosterone levels within a relatively narrow range.
Everything changes when you introduce anabolic steroids, though.
The sudden surge in testosterone causes the hypothalamus to drastically reduce GnRH production, which shuts down LH and FSH production and halts natural testosterone production.
Within days of taking steroids, natural testosterone levels plummet, and over several months, your testicles shrink.
In the case of Winstrol, the suppressive effect on testosterone is sizable. For instance, in a study published in Clinical Endocrinology, men given 10 mg of Winstrol daily for 2 weeks saw their testosterone levels fall by 55%.
The only way to restore natural testosterone production and testicle size is to stop taking steroids. Even then, it can take several months before testosterone levels and testicle size return to normal.
